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Harvard-MIT Math Tournament #0i5d

Harvard-MIT Math TournamentHard

From module Homothety and Spiral Similarity

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Understand the scale
Scale 0.5: Easiest math competition problems, often solvable even for early middle school students without experience. 1: Problems strictly for beginners, often at a moderate middle school level. 1.5: Problems for stronger beginner students, on the level of the middling problems in most middle school contests. 2: For motivated beginners, harder questions from the previous categories. 2.5: More advanced beginner problems, hardest questions from previous categories. 3: Early intermediate problems that require more creative thinking. 3.5: Tougher early intermediate problems that consistently stretch into higher-level creative thinking or conceptual knowledge. 4: Intermediate-level problems. 4.5: Upper intermediate problems approaching the upper bound for non-invitational sprint math competitions. 5: More difficult AIME problems or simple proof-based Olympiad-style problems. 6: High-level AIME-styled questions or introductory Olympiad-level questions. 7: Tougher Olympiad-level questions, may require more technical knowledge. 8: High-level Olympiad-level questions. 9: Expert Olympiad-level questions. 9.5: The hardest problems appearing on Olympiads which the strongest students could reasonably solve. 10: Historically notorious problems, generally unsuitable for even very hard competitions because they are exceedingly tedious, long, and difficult.
HomothetyDistance chasing

Problem

Problem:

Two circles have radii 1313 and 3030, and their centers are 4141 units apart. The line through the centers of the two circles intersects the smaller circle at two points; let AA be the one outside the larger circle. Suppose BB is a point on the smaller circle and CC a point on the larger circle such that BB is the midpoint of ACAC. Compute the distance ACAC.

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